1. Field of the Invention
This invention relates to an oscillator circuit, and, in particular, to an oscillator circuit using charges and discharges of a capacitor, and an integrated circuit incorporating the same.
2. Description of Related Art
Japanese Unexamined Patent Application Publication No. 10-233657 discloses a CR (capacitor-resistor) oscillator circuit using charges and discharges of a capacitor. This oscillator circuit comprises a capacitor and a comparator, wherein one input terminal of the comparator is supplied with a reference voltage and the other input terminal is supplied with the voltage generated by charging and discharging the capacitor, and the comparator outputs the results of the comparison as the oscillation signal. In this circuit, the reference voltage is switched between a lower reference voltage and a higher reference voltage based on the generated oscillation signal. The operation of charging and discharging the capacitor is also controlled based on this oscillation signal.
In the above-mentioned CR oscillator circuit, the period of the oscillation is determined only by the conditions of one terminal of charging and discharging the capacitor. In order to have a longer period with this oscillator circuit, a capacitor with higher capacitance is required. Such a capacitor, however, takes a larger area, which causes the problem of the increasing cost of the chip.